I will throw my 2 cents in, for whatever it is worth. Before, though, here is my bona fides. I spent 24.5 years in the United States Army as an Infantry Officer, Ranger qualified, and spent 11.5 of those years stationed in the 10th Mountain Division (Light Infantry) in Fort Drum, NY, where I now live as a retired lieutenant colonel and work on post as a contracted military trainer. I also run the Shubu Kan Dojo on post (FB: @shubukanURKA). I deployed 6 times (3 x operational: Panama, Kosovo, Bosnia // and 3 x combat: Afghanistan, Iraq, Iraq) for a total of 3 years and 5 months. My last job in the Army was as a light infantry battalion commander, where I emphasized combatives training to the max for the entire unit. I agree that cross training can be good, but the styles and types you train depends on what you are preparing for. Training for combat is different than training for a MMA fight, which is different than training for street self defense, which is different from point sparring, which is different from, etc. etc. In combat, you kill with your primary weapon, then your secondary weapon, then an improvised weapon (like a helmet, entrenching tool) or knife, and then with your hands, feet, head. The last thing you want to do is go to the ground with all of your equipment and body armor, it does not matter how skilled you are in BJJ. If your opponent is an insurgent and is not wearing heavy equipment he will mop the floor with you and probably pull something off of your kit that he can use against you. Additionally, punches and kicks are going to be somewhat limited based on the equipment you are wearing and those things can take a while to subdue a foe. Punching and kicking combined with vital point strikes, joint locks, and dirty moves (biting, eye gouging, head butting, hair pulling, pinching, whatever works) is the best way to fight if you have to do so without weapons. However, none of that will work within the rules of MMA or point sparring. In MMA you must be cross trained because, based on the rules of the game, you have to be. On the street, I would argue that you want to subdue your opponent as quickly as possible. Again, this means punching and kicking combined with vital point strikes, joint locks and dirty moves. Going to the ground in this scenario is not a good idea because your aggressor may have friends who will stomp on your head (not good). That does not mean ground fighting is only important for MMA. it is good to have ground fighting and BJJ/Catch Wrestling to enable you to fight if you do get taken to the ground. But, for what I have prepared for (combat), stand up, vital point strikes, joint locks, and dirty moves were more of a focus.